Pakistan´s secret service ISI behind the 11th September 2001 attacks?

One thing that can be said against this is that the ISI spent a long time to
bring the Taliban on power in Afghanistan, and certainly they knew that
the movement´s fall from power would be quite likely after a major attack
against the US that could be linked to al-Qaida, which the movement let
to operate freely and establish training camps in the areas of Afghanistan
that Taliban controlled.

But of course puppets can sometimes cut their leashes and become
independent operators, which may force their former masters to took
drastic action and the Pashtuns that form the majority of the Talibans
have long harbored dreams of uniting the Pashtun lands that are now
divided between Afghanistan and Pakistan.